1. Field of the Invention
The present invention relates to an optical recording/reproducing apparatus for optically recording a signal on a recording medium (a disk) and/or for optically reproducing the recorded signal by using a light beam from a light source such as a laser. More particularly, the present invention relates to an optical recording/reproducing apparatus equipped with a digital signal processor which is used for the control of a light-beam spot such as focus servo for converging a light beam on a recording medium in a predetermined convergence condition and tracking servo for allowing the light-beam spot to precisely scan a track on the recording medium.
2. Description of the Related Art
An optical recording/reproducing apparatus for recording and/or reproducing information on or from a disk-like recording medium (hereinafter simply referred to as a disk) such as an optical disk and a magneto-optical disk applies a light beam onto a desired track on the disk, and detects the information on the basis of the reflected light beam. Accordingly, in such an apparatus, it is necessary to precisely converge the light beam on the desired track in a predetermined convergence condition. The control of the light-beam spot is performed by a disk-drive control device.
A disk-drive control device is provided with filters for servo systems such as focus servo for converging the light beam on a recording medium in a predetermined convergence condition and tracking servo for allowing the light-beam spot to precisely scan a track on the recording medium. In a conventional disk-drive control device, such servo-system filters are implemented as digital filters which perform operations. The disk-drive control device includes two processors. One of the processors is a digital signal processor (hereinafter referred to as a DSP) including digital filters. The other is a central processing unit (hereinafter referred to as a CPU) which performs the control of the whole disk drive including the DSP and performs the management of communication and data transfer between a host computer and disk drive in the optical recording/reproducing apparatus. The configuration of the conventional disk-drive control device equipped with the CPU and the DSP is shown in FIG. 10.
A CPU 303 sends commands such as focus-servo 0N (FCON) end tracking-servo ON (TRON) to a DSP 302 in order to perform the recording or reproducing of information, in accordance with the requirement from a host computer 301 of an optical recording/reproducing apparatus. When the DSP 302 receives these commands, it allows the focus servo and tracking servo to operate, and accordingly controls a focus actuator 131 and a tracking actuator 103 so that a light beam follows the desired track on a disk. When a SEEK command is sent from the CPU 303, the DSP 302 drives a moving device, for example, a linear motor 304 for moving an objective lens (not shown), the focus actuator 131, the tracking actuator 103, and the like in a radius direction of the disk. In this way, the seek operation for a desired track onto or from which the information is to be recorded or reproduced.
In the DSP 302, gains or phases of frequency characteristics of filters used for focus servo and tracking servo are determined in view of the sensitivity of the moving device such as an actuator and a linear motor used in the disk drive, and frequency characteristics of a movable portion such as a resonance frequency. The movable portion is a portion including a head and at least one actuator for moving the head. The software of the DSP 302 is set so that digital filters which perform the operations in accordance with the software have the determined frequency characteristics. Thereafter, the software of the DSP 302 serves as a mask ROM. Accordingly, if the types of actuators used in respective models of disk drives are different from each other, the DSP cannot be used in common among the different models of disk drives, but it is necessary to provide original or dedicated DSPs for the respective models of disk drives. Moreover, it is necessary to design the hardware and the software of the CPU which controls the DSPs, in accordance with the types of the DSPs. This means that it is necessary to provide CPUs respectively for corresponding types of DSPs.
In recent years, the optical recording/reproducing apparatus is required to include a plurality of disk drives in one housing for the purpose of media conversion or backup. As shown in FIG. 11, in such an apparatus, each of the plurality of drives includes a head for a corresponding one of various media such as CD, 3.5" MO, 5" PCR, PD, and MD. In such an apparatus, original or dedicated DSP and CPU corresponding to the type of the head are provided in each drive, and a further CPU for managing the whole of the plurality of drives is required. Accordingly, the production cost of the apparatus including a plurality of drives is very high.
A recording/reproducing apparatus dedicated for one kind of medium which is a general type such as an MO recording/reproducing apparatus or a PD recording/ reproducing apparatus is equipped with one head, and one DSP and one CPU for controlling the head. Such a general type of recording/reproducing apparatus also has, for example, the following drawback. In order to develop the models, if the specifications of a head or the specifications of an actuator are changed for reducing the production cost, or for improving the characteristics, it is necessary to accordingly change the software of the DSP. However, the software of the DSP is implemented as a mask ROM, so that it is very difficult to change the software. In order to widely and easily accommodate the change of specifications of the head and actuator, it is required that various kinds of software for allowing the change of specifications are stored in the ROM of the DSP. This necessitates the memory having a very large capacity. Therefore, the production cost of the DSP itself is high, and hence the production cost of the whole apparatus is correspondingly high, too.